1. Field of the Invention
This invention relates to an energy conversion element, and more particularly to an element for converting light and thermal energies into electrical energy.
2. Description of the Prior Art
Conventionally, a photocell utilizing a semiconductor element such as silicon, gallium arsenide or the like has been used to convert solar light energy directly into electrical energy, whereas the conversion of solar thermal energy directly into electrical energy has been carried out using a semiconductor element of the PN junction type.
However, such conventional energy conversion elements unfortunately have a disadvantage of being substantially poor in conversion efficiency. More particularly, the photocell cannot absorb light other than light of a short wavelength corresponding to band gap energy of a semiconductor used therein, resulting in the energy conversion efficiency being significantly decreased. For example, a monocrystalline silicon solar battery which is now put into practical use has an energy conversion efficiency of up to 12%. The conventional element for converting thermal energy into electrical energy has an energy conversion efficiency of 3-4% based on its theoretical value, thus, it cannot be substantially put into practical use except for the purpose of thermometry.